Status of LHC Operations

R. Assmannfor the LHC commissioning team and LHC teams & groups

LPCC 23.4.2010

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Commissioning Strategy Last Weeks

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Mike Lamont et al

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Outline

The squeeze story: Getting all 4 IR’s squeezed to 2m IR1 and IR5 IR8 IR2 All 4 IR’s at once Qualification tests for machine protection

Higher intensity Storing 10 bunches at injection Storing nominal bunch charge

Feedbacks, emittance and operational issues Feedbacks “Hunt the Hump” Multiple beam-induced quench

Conclusion

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PART I – Squeeze IP Beam Size @3.5 TeV

23.4.2010

… a long story but with a happy ending…

This is one of the most complex stages of operation!

Change of beam optics to reduce beam size at the interaction points.

Goal for 2010 beam size reduction: factor ~2.2 for each plane(factor 5 in IP beta):

factor 5 higher luminosity

This is a change in b* by a factor ~5! Complex control of all IR power converters plus precision corrections.

At the same time the beam size at the triplets around the experiments increases significantly:

triplets become aperture bottlenecks

Protection of triplets and experiments against beam loss must be carefully verified before stable beams.

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Step 1: Squeezing and correcting IR1 & IR5

b-beat for Beam1 @ b * = 2m after correction using IR5 Q2:

Rogelio Tomas et al23.4.2010

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Example: CMS Luminosity Optimization

23.4.2010S. White

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ATLAS and CMS Improvement

23.4.2010

M. Ferro-Luzzi

Increase after squeeze: Factor 4-4.5 (to be compared with expected factor 5)

Luminosity up to 5×1027 cm-2 s-1.

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Step 2: Squeezing and correcting IR8

b-beat for Beam1 after squeeze and @ b * = 2m in IR8 after correction of Q5:

Rogelio Tomas et al23.4.2010

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Step 3: Squeezing and correcting IR2 b-beat for Beam1 at b* = 2m in IR2 (all other IPS at b * = 2m):

Rogelio Tomas et al

23.4.2010

Problem Example I: Too steep current requests

RQS.A78B2 (17/04) tripped 3 times due to steep current-ramp requests. RQS.A56B2 (16/04) tripped once for the same reason QPS inductive compensation does not have time to react. V_REF translates directly into U_RES which goes above threshold. Functions need to be adjusted / smoothened.

Fixed as found… Thanks to crucial help from MP3 team on shift!

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Problem Example II: Discontinuities after incorporation

Fixed by new software

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Problem Example III: Leftover trims incorporated

Fixed by procedure…

Many small issues that require to be found and fixed. Each little issue costs 5-6 hours!

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Step 4: Squeezing and correcting all 4 IR’s

23.4.2010

Mike LamontGabriel MullerMarek StrzelczykStefano RedaelliXavier

21 optics steps!

Rogelio Tomas et al

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Squeeze now starts working smoothly!

23.4.2010

Look at 4 most recent fills in last 48 hours!

All these fills made it to 3.5 TeV and 2m b*!

First two still affected by bugs (intensity loss) but used for qualification study!

Last two fills without any problem, very smooth! Used for provoked loss tests in preparation for stable beams!

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Provoked vertical beam loss on beam 1

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IR8 IR1IR2 IR5

Mom

entu

m C

lean

ing

Dum

p P

rote

ctio

n C

ol.

2m optics exposes IR’s as expected! Protected by tertiary collimators.

Collimation Team

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Zoom (vertical loss beam 1)

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factor 1,000

factor 4,000

Betatron Cleaning

IR8factor 600,000

OK for stable beams from collimation!Collimation Team

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Provoked asynchronous beam dump

1e-3 leakage to tertiary collimators in IR’s

OK for stable beams from beam dump!

Brennan Goddard et al

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Status and Outlook Squeeze

Squeeze to 2m for all 4 IR’s established. All IR’s steered into collision. Golden orbit established. All 16 tertiary collimators adjusted. Squeezed optics fully qualified for protection.

Next: intensity from 2e10/beam to 3.5e10/beam Next: Stable beams with 10 times luminosity:

1028 cm-2 s-1 in reach

Still a lot to go but first steps are most difficult!

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PART II – Increasing Intensity at 450 GeV

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… will be a long story but so far very happy…

This will be the challenge of LHC!

Goal: Factor 10 at injection.

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Increase Intensity: Number of Bunches

LPCC, R. Assmann

Dump of the 10 bunches

T factor 10

Brennan Goddard et al

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Increasing bunch intensity

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factor 10

Major success for LHC: Nominal bunch charge at 450 GeV! 25 hours beam lifetime!

Means: No single bunch show stoppers from dynamic aperture, instabilities, …

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Increase Intensity: Over-Injection

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Example of over-injection of 1E11 – 40 us integration

Losses from over-injectionLosses from TL

collimators (X-talk)

TDI

Brennan Goddard et al

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Tunnel View

Collimation Team

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Transfer line collimator

Ring magnets with beam loss monitors

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Increase Intensity: Emittance

Emittances versus bunch intensity:

factor 10beyond 1e10 pilot

Injection team

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Increase Intensity: Tune Shift Beam 1

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DQv = 0.0015

DQh = 0.0005

Injection team

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Tune shift: Measured versus Expected

B1 meas B2 meas ExpectedQh tune shift 5e-4 1.5e-3

Qv tune shift 1.5e-3 2.0e-3 4.5e-4

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for 1e10 to 1e11 p

Elias Metral et al

to be studied systematically:

impedance vs. collimator settingsother source?

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PART III – Feedbacks, Emittance & OP Issues

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…the cure, some issues…

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Tune Feedback in Operation

Tune feedback during ramp: Ralph Steinhagen et al

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Orbit Feedback in Operation

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Ralph Steinhagen et al

Maximum orbit change during energy ramp: 0.08 mm

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Transv. Damper: Damping Beam Excitations

OFF ON

Crucial device to keep emittance

growth under control!

Wolfgang Hoefle et al

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Emittance Growth: Still a Problem

Mirko Pojer23.4.2010

factor 3

Emitt

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Time

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Lifetime Drops with “Quiet” Beam Our friend the hump on the lifetime - ~ 7 minute period

LPCC, R. Assmann

Hunt the Hump!The hump is a vertical excitation on the beam that has a fast frequency component (therefore visible as “hump” in the tune spectrum and a slow moving frequency component (7 min).

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4 Magnet Quench from Injected Pulse Losses in Sector12 at 450 GeV injection (1e10 p):

Debugging of operational procedures…

First injection into machine with some magnets mis-powered.

First injection always with pilot beam to exclude damage.

Collimation cannot protect for strong local kicks!

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Conclusion Our “baby” (the LHC) learns walking surprisingly fast:

Routine ramps with 2e10 p to 3.5 TeV (just below safe beam limit). Squeeze in all 4 IR’s to 2m b* starts to run smoothly (smallest 2010). Squeezed optics fully qualified for protection IR’s protected by

collimation as foreseen. Tonight/tomorrow:

Stable beams: unsafe 3.5 TeV beam, all IR’s squeezed to 2m b*.Luminosity at 1028 cm-2 s-1.

In parallel important progress towards higher intensities: Stored nominal bunch intensity at 450 GeV with excellent lifetimes. Multiple bunches stored. Various feedbacks running. Instrumentation, RF, cryo, … very good! Seeing and addressing issues: emittance growth, hump, thresholds,

impedance, operational issues, … Remember, LHC is still a baby (for beam). So we try to guide

it carefully the first steps… (we do not want to fall)23.4.2010

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Thank you for your attention!

23.4.2010